FIG. 6.

Acetylation of H3 and H4 histones at μ enhancer-distal and -proximal positions in T3T7 transgenes. Chromatin extracts from formaldehyde-cross-linked MPE-T3T7 and PE-T3T7 transgenic pre-B cells were immunoprecipitated as described for Fig. 5. In the pre-B-cell lines used in these experiments, the transgenes are integrated in transcriptionally inactive chromatin (33). Transgene-specific sequences in the immunoprecipitated chromatin and input DNA were quantitated by PCR assays. Specific primers were used for amplification of ∼350-bp DNA fragments that include either the distal T7 region, the proximal T3 region, or the endogenous mb-1 promoter as an internal control. Eight serial fourfold dilutions of the template DNA were used to allow a semiquantitative PCR. The distal T7 region of the MPE-T3T7 transgene was immunoprecipitated with α-AcH4 antiserum with a higher efficiency than that of the PE-T3T7 transgene.